Objective To determine whether hearing loss is associatedwith incident all-cause dementia and Alzheimer disease (AD).
Design Prospective study of 639 individuals who underwentaudiometric testing and were dementia free in 1990 to 1994.Hearing loss was defined by a pure-tone average of hearing thresholdsat 0.5, 1, 2, and 4 kHz in the better-hearing ear (normal, <25dB [n = 455]; mild loss, 25-40 dB [n = 125];moderate loss, 41-70 dB [n = 53]; and severe loss,>70 dB [n = 6]). Diagnosis of incident dementia wasmade by consensus diagnostic conference. Cox proportional hazardsmodels were used to model time to incident dementia accordingto severity of hearing loss and were adjusted for age, sex,race, education, diabetes mellitus, smoking, and hypertension.
Setting Baltimore Longitudinal Study of Aging.
Participants Six hundred thirty-nine individuals aged36 to 90 years.
Main Outcome Measure Incident caces of all-cause dementiaand AD until May 31, 2008.
Results During a median follow-up of 11.9 years, 58 casesof incident all-cause dementia were diagnosed, of which 37 caseswere AD. The risk of incident all-cause dementia increased loglinearly with the severity of baseline hearing loss (1.27 per10-dB loss; 95% confidence interval, 1.06-1.50). Compared withnormal hearing, the hazard ratio (95% confidence interval) forincident all-cause dementia was 1.89 (1.00-3.58) for mild hearingloss, 3.00 (1.43-6.30) for moderate hearing loss, and 4.94 (1.09-22.40)for severe hearing loss. The risk of incident AD also increasedwith baseline hearing loss (1.20 per 10 dB of hearing loss)but with a wider confidence interval (0.94-1.53).
Conclusions Hearing loss is independently associated withincident all-cause dementia. Whether hearing loss is a markerfor early-stage dementia or is actually a modifiable risk factorfor dementia deserves further study.